This invention relates to an improved apparatus and method for cleaning large tanks or vessels, such as, for example, automotive and railway tank cars.
It is imperative in many industrial operations to thoroughly clean the interior surfaces of large tanks or vessels. Such cleaning is usually done by manual labor. But, manual cleaning is a tedious and time consuming task. Furthermore, manual cleaning may expose the worker to toxic or corrosive substances and vapors and otherwise create a hazardous environment for the worker. Thus, automatic cleaning apparatus and methods are desirable.
The phosphoric acid industry presents a typical large tank or vessel cleaning situation. Phosphoric acid is shipped in rubber-lined automotive or railway tank cars having only a small access opening at the top. Gypsum and other solids precipitate during the period of transportation from the acid manufacturing plant to the ultimate destination. As a result of such precipitation, a sticky, acid-rich sludge is deposited on the sides and bottom of each tank car. Because the amount of sludge present in each tank car is often substantial, standard industry practice is to clean or remove the sludge from the interior surface of each tank car after each round trip made by the car.
Various apparatus and methods for cleaning automotive and railroad tank cars and other large tanks or vessels have been proposed. Some of the proposed apparatus and methods, such as shown in U.S. Pat. No. 3,895,756, are routinely used in industrial cleaning operations.
Each of the known apparatus for cleaning large tanks or vessels has one or more major disadvantages. For example, known apparatus are either too large or too heavy, or both, for one worker to conveniently move the apparatus from location to location and position it over and in the access opening at the top of the tank or vessel to be cleaned. And, known apparatus are incapable of thoroughly cleaning the entire interior surface of a typical large tank or vessel, such as, for example, an automotive or railway tank car. Furthermore, known apparatus either cost too much to manufacture or clean too slowly, or both, for economical cleaning of large tanks or vessels. These disadvantages are not inherent in the present invention.
The apparatus of the present invention is comprised of a fixed support frame and a tiltable frame which is pivotedly mounted above the support frame. A wash nozzle assembly for insertion through the access opening of the tank or vessel to be cleaned and into the tank or vessel is pivotedly mounted to the tiltable frame. The wash nozzle assembly is comprised of a spray head having at least one pair of opposed spray nozzles and a cleaning liquid inlet tube. One end of the cleaning liquid inlet tube remains outside the tank or vessel to be cleaned and is connected to a source of pressurized cleaning liquid by a flexible hose or other suitable liquid supply line. During operation of the apparatus, the wash nozzle assembly is pivoted back and forth at an operator controlled rate to direct cleaning liquid spray jets along the longitudinal axis of the tank or vessel to be cleaned. At the same time, the tiltable frame upon which the wash nozzle assembly is pivotedly mounted is tilted at an operator controlled rate to direct the cleaning liquid spray jets along the latitudinal axis of the tank or vessel. The combination of these two basic movements washes the entire length and width of the tank or vessel to be cleaned with spray jets of cleaning liquid.
To achieve these basic movements, a motor or engine drives a first gear box which pivots the wash nozzle assembly by means of a lever arm mechanism. The first gear box drives a second gear box which tilts the tiltable frame by means of a lever arm mechanism. A conventional drive shaft mechanism is the preferred means for operatively connecting the motor or engine and the first gear box. A conventional belt and pulley mechanism is the preferred means for operatively connecting the first gear box and the second gear box. For safety reasons, an air motor connected to a remote air supply source by a flexible air hose is the preferred motor or engine. The motor and the first and second gear boxes are fixedly mounted to a tiltable frame.
The wash nozzle assembly of the present invention features a spray head having at least one pair of opposed spray nozzles. The opposed spray nozzles create opposing forces which result in substantially lower total stress levels in the various components of the apparatus than would be present if a single spray nozzle or a plurality of unopposed spray nozzles were utilized. For that reason, the apparatus of the present invention can be manufactured from components which are small enough and light enough to enable one worker to conveniently move the apparatus from location to location and position it over and in the access opening at the top of the tank or vessel to be cleaned.
The preferred embodiment of the apparatus of the present invention features two alternate spray heads for the wash nozzle assembly. One of the spray heads is comprised of two spray nozzles having an angle of approximately 80.degree. there between. That spray head has proved to be particularly useful for breaking up and flushing out hardened sludges in the bottom of railway tank cars at a faster rate than is possible with known apparatus. The other spray head is comprised of three pairs of opposed spray nozzles. That spray head has proved to be particularly useful for rapidly cleaning liquids and easy to remove solids from the entire interior surface of railway tank cars.
The apparatus of the present invention can be manufactured from simple mechanical components which are available from commercial sources. Accordingly, the apparatus of the present invention is more economical to manufacture than known apparatus.